Which of the following diseases is confined to Pintos and Paints?

Lethal white syndrome is a genetic condition that is specifically associated with Paint and Pinto horses. It arises from a genetic mutation that affects the development of the gastrointestinal tract. Foals born with this condition typically have a pure white coat due to the overo color pattern and suffer from severe developmental issues, leading to their inability to survive past a few days after birth. The condition is characterized by a lack of functional intestines, which makes it unique to these specific breeds that carry the genetic predisposition.

In contrast, the other diseases listed are not confined to Pintos or Paint horses. Equine Infectious Anemia can affect horses across various breeds and is transmitted through blood, often by biting insects. West Nile Virus and Equine Influenza are also not breed-specific and can infect any horse, regardless of its breed or coloring. Thus, only Lethal White syndrome is particular to Pintos and Paints, making this the correct choice.